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SkyLifter is an eVTOL air crane

skylifter.eu

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Re: SkyLifter is an eVTOL air crane

#11

Post by masklinn »

0x_rs wrote: post #6

Lighter-than-air is still largely untapped territory today, and it's a shame because it should scale in size very well. Without going straight away into more ambitious projects that were fantasized the past century [0], I'd love for a resurgence of it. 0. https://en.m.wikipedia.org/wiki/Cloud_Nine_(sphere)

Tons of companies over the years have taken a shot at it (CargoLifter, Aeros, Walrus HULA, HAV).

Turns out, so far, it's all been pretty shit, because outside of super specific niches airships are so slow they need to be much cheaper than aircraft, but the upfront costs to create massive-enough airships to even have a chance makes it a difficult proposition.

Re: SkyLifter is an eVTOL air crane

#14

Post by lifeisstillgood »

I am trying to avoid being negative here but lifting 250 tonnes in remote / difficult areas is a serious challenge.

The lift is not so much the problem (although that's a big balloon) - fighting wind sheer will require stupendous amounts of power. Especially as wind is pressing not just at that cargo but at the balloon itself. And anywhere that's remote / inaccessible almost always comes with lots of wind.

Hmm, actually lift might be a problem ...

So to get 250 000 kg off the ground takes a volume of helium balloon (if the below site is right) of 250,000m3 (it seems to be fairly linear)

(this seems intuitive - air "weighs" about 1.2kg /m3 sea level, so a vacuum of 1m3 could lift 1.2kg. )

that is 100mx100mx25m ! that's the inner part of any athletic stadium. That's insane surely?

https://www.engineeringtoolbox.com/hot-air-balloon-lifting-f...

Re: SkyLifter is an eVTOL air crane

#15

Post by nuccy »

wepple wrote: post #12

Can somebody explain to me how it is able to hover (suggesting it is neutrally buoyant in air) but then attach a load and overcome the weight?

Basically two methods:

1) have counterweights (e.g. as mentioned above for another similar concept Cargolifter which used water);

2) expand its volume during loading and contract after unloading. E.g. pumps compress gas while unloading and release it back while loading.

These two options are obviously the same thing - change the vehicle density to adjust the buoyancy but implemented with and without external weights. Submarines do this also by filling the ballasts tanks with either water or flushing them with compressed air.

Re: SkyLifter is an eVTOL air crane

#16

Post by Toutouxc »

joenathanone wrote: post #13
wepple wrote: post #12

Can somebody explain to me how it is able to hover (suggesting it is neutrally buoyant in air) but then attach a load and overcome the weight?

It can just swap weight(s).

So instead of having to move your 25 ton cargo around, you now have to move your 25 ton ballast to be swapped for the cargo at the drop off point so the SkyLifter doesn't yeet itself into stratosphere.

The FAQ and literally everything else about this project is vague, disappointing and a little fishy.

Re: SkyLifter is an eVTOL air crane

#17

Post by capableweb »

CoChiefResident wrote: post #9
Roritharr wrote: post #7

Earlier quoted context omitted.

CargoLifter for me personally marks the beginning of the German Decline in Engineering. The reasons for why it failed are the same reasons why we have such large problems with infrastructure projects and are falling behind in innovative technology. It's a very sad read.

If I remember correctly, Cargolifter failed to have a straightforward loading and unloading method. The airship is designed to lift a certain amount of weight, which has to be replaced as soon as you dismount the cargo. Cargolifter used water which was transported to the destination site via trucks. I only had a quick glance at the SkyLifter website, but I did not find any solution for that problem.

It seems surprising to me that there is not more information on the website regarding what gas this gas-filled lenticular-shaped aerostat thing is floating with. I understand they are aerostatic and the gas needs to be lighter than air, but that doesn't leave many options that are not helium I guess. And then in order to drop whatever they haul down, they'll need to either let it escape or contain it somewhere else, or spend energy at keeping it down somehow.

Re: SkyLifter is an eVTOL air crane

#18

Post by wcoenen »

wepple wrote: post #12

Can somebody explain to me how it is able to hover (suggesting it is neutrally buoyant in air) but then attach a load and overcome the weight?

I was wondering about the same thing. It doesn't seem to be explained on the company site.

The only thing I could come up with is to have neutral buoyancy air blatters that can expand/contract. These would be inside the volume of buoyant gas but connected to the outside air. Then pump the buoyant gas into a pressure tank to reduce buoyancy, or release it from the tank to increase buoyancy.

Re: SkyLifter is an eVTOL air crane

#19

Post by CraigJPerry »

lifeisstillgood wrote: post #14

I am trying to avoid being negative here but lifting 250 tonnes in remote / difficult areas is a serious challenge. The lift is not so much the problem (although that's a big balloon) - fighting wind sheer will require stupendous amounts of power. Especially as wind is pressing not just at that cargo but at the balloon itself. And anywhere that's remote / inaccessible almost always comes with lots of wind. Hmm, actua…

>> that is 100mx100mx25m

That’s huge!

I wondered how big was the hindenberg, wiki claims 245m long and 41m wide, and 41m tall (excl. cabin). Only 200k litres of gas capacity. 232k tonnes lift.

Re: SkyLifter is an eVTOL air crane

#20

Post by masklinn »

krisoft wrote: post #5
H8crilA wrote: post #2

This will be a pain in the ass to manage in controlled airspace because it's so much slower than anything else. But I guess it would also use different flight levels, so maybe not a problem at all. I wonder how does the fuel usage compare to a plane, that's the real measure of green-ness.

I think comparing it to a plane is misplaced. They call it a crane. Presumably the load and the craft arrives on a truck and you use it to hoist the load up the last few maybe hundreds of meter max. Do i read that wrong? Edit: yes! I was reading that wrong. To quote the relevant part: “SkyLifters fly from job to job, so they can do work in locations that would be challenging for land cranes.”

> Presumably the load and the craft arrives on a truck

Nah they're absolutely gigantic and usually semi-rigid (especially if you have solar panels on top).

SkyLifter seems very cagey about the purported crane's dimensions (couldn't find anything on the subject), but the Airlander 10 (which I understand only lifts 14t) is 90 x 43 x 26... meters.

IIRC the rule of thumb is that you need 1m3 of helium to lift 1kg, to lift just a 250t payload you thus need 250000m3 of helium.

According to skylifter's "design" page the lenticular envelope has a height of 1/4th the diameter (3 units wide, 0.75 units deep). For a cylinder that's 108m wide and 27m high, so taking in account the lenticular shape we might be closer to 120m/30m (400ft wide by 100ft high). That's the size of a baseball field, and 14 stories high.

And that's only taking the payload in account, not the solar panels, not the cabin, not the engines, ...

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